This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Research is performed to elucidate toxicology and pharmacokinetics of thiol-capped CdSe, CdS, PbSe and PbS quantum dots (QDs) in vivo. Efforts have focused on the development of analytical and instrumental methods for as well synthesis of stable thiol-capped CdSe nanoparticles and their characterization. Two different routes were utilized for producing CdSe NPs in that we either used thioglycerol or mercaptoacetic acid for stabilizing the NPs. In either scenario, thiol-capped CdSe NPs were highly stable for months under ambient conditions. Purification studies were also completed. Characterization was performed with UV-visible spectrometry and TEM. Data indicated that size could be varied from 2-4 nm by varying the amount of accping agent or selenium. Stability tests were under sonication in different solvents. Particles were highly stable in water under ultrasounds, but exhibited instability in alcohol and acidic media resulting aggregation. Effect of the media was examined on the extraction of ionic Cd from animal tissues for speciation of ionic Cd and CdSe from the animal organs. Water and ethanol were unsuitable for extraction of Cd from biological tissues. Extraction achieved in acid media, however, the use of acid resulted in decomposition of CdSe NPs that introduced additional ionic Cd to solution. Tetramethylammonium hydroxide (TMAH) was found to be suitable for extraction. Extraction efficiency was ranged between 85-100% when testetd with liver reference material (DOLT-4). Treatment of CdSe NPs did not induce and degradation of Cd from NPs to solution ultrasounds, nor did cause any degradation during TMAH digestions. The differences in Cd signals from untreated and treated CdSe NP solutions were statistically insignificant. Preliminary data is reported to get an insight into the distribution of Cd and CdSe NPs in organs. Data indicated that majority of CdSe is in the form of ionic Cd in the organs (liver and kidney). Exposure of NPs to light induces enhancement on the levels of ionic Cd.